Romain Grosjean, Felipe Massa and Felipe Nasr have expressed their frustration at being forced to run 'joke' tyre pressures following free practice for the Belgian Grand Prix as temperatures soared at Spa-Francorchamps.

On a day that saw track temperatures exceed 40 degrees - considerably higher than usually seen at the Belgian venue -, drivers complained of a lack of rear grip compounded by lofty pressures.

RESULTS: Belgian Grand Prix - Free practice results (2)

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Having complained to Pirelli about tyres pressures this year already, Romain Grosjean led the calls for them to be reduced again, saying his tyres are 'giving up' on his Haas mid-corner.

"I have to do a job and push as hard as we can, honestly I'm not too happy with the tyre behaviour because it's such an amazing track where you can really feel the strengths of a Formula 1 car, and you can't really get it as much as you like due to that.

"You're in the middle of the corner and suddenly they give up, the front and rear, and it's not very fun. But it's the same for everyone so it's up to us to find a solution and go faster around that."

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Massa was similarly critical, labelling the pressures as a 'joke'

"One of the issues [on the Williams] is the tyre pressures. I've never run such high tyre pressures like we have, to be honest in my whole career. This is a bit of a joke to be honest."

Some were less sympathetic though with Manor's Pascal Wehrlein pointing out that the pressures are the same for everyone and that you need to adjust your driving style accordingly.

"It is the same for everyone. You cannot push two laps in a row, you have to do a cool down lap and the rear tyres especially are overheating pretty quickly."

Sauber driver Nasr reckons the pressures will be changed once it is raised in the drivers' briefing.

"I'll speak to the others and see what they say. Maybe, we will have to see. We have seen that before sometimes we gain a few psi back but let's see."

Pirelli, meanwhile, says it will conduct analysis before deciding on whether to tweak the pressures, though Mario Isola says the teams shouldn't have been caught by surprise.

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"The procedure is the usual one, so we are receiving now the telemetary from the team's and we compare with the simulation," Isola said. "I have to say, it's not a surprise for these teams to have these kinds of pressures here, because at the beginning of the year we decided to take some representative high-energy circuits - one of which was Spa - so they knew in February that the plan for Spa was to have around 23-24 PSI front, and 22 rear.

"It was 24PSI and with the updated simulation we went down to 23.5, it's not a big difference but it's not higher than expected. Now we check with the usual system, the telemetry data. If we have room to do down, we go down.

"Maybe we have to increase if the severity of the telemetry is higher than the simulation... They have three hours to upload the data and we have three hours to analyse the data. So at 9.30 we are going to confirm or change prescriptions."

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